Stacked sheet separating and gripping apparatuses of this type are known in the art. See, for example, Japanese Patent Publication No. Sho 55-42023.
To better understand the background of this invention, a conventional stacked sheet separating and gripping apparatus will be briefly explained with reference to FIG. 23. In this device, a plurality of sheets S in a stack are laid on a stacker 51 and then urged upwardly by a take-up or a drag roller 53 which abuts against the stacker and which is positioned on its periphery. The drag roller 53 contains a plurality of flexible bristles 52 that radially extended from its surface.
A gripper or holder 54 is positioned at an incline to form a certain angle with the top of the stacked sheets. The gripper 54 includes a plurality of needle-like projections 55 extending from its surface.
The take-up or drag roller 53 is adapted for clockwise rotation to allow the bristles 52 to pick up and draw some of the upper sheets and deliver the uppermost sheet inside out to the gripper 54 when the roller is moved along a guide groove 56 that is parallel to the gripper 54.
When the roller 53 reaches the end of its travel and places the leading edges of the sheets on the gripper 54, the roller 53 is rotated in reverse to return to its lowermost position, leaving the uppermost sheet engaged with the projections 55 and retained on the gripper 54, while other sheets are returned to the stacked sheets S. Thereafter, the sheet on the gripper 54 is conveyed by a separately mounted gripper and conveyor mechanism to a predetermined station, and released.
Another known approach, as shown in FIG. 24, uses a take-up roller 61 having a plurality of bosses to abut against a stack of sheets S. The take-up roller 61 is rotated to bend the uppermost sheet into a loop in a clearance 64, defined by a stationary support 62 and a holder lever 63. Holder level 63 raises the loop from the sheet surface so that a spring 65 pivots the holder lever 63 about a shaft 66 to hold the loop between the stationary support 62 and the holder 63. A similar apparatus can be found, for example, in U.S. Pat. No. 3,940,125.
The conventional stacked sheet separating and gripping apparatuses discussed above require two independent and individual actuators with respect to rotation and displacement of the take-up rollers rendering the structures complicated, and involving troublesome operation.
Furthermore, these apparatuses lack a simplified means for gripping the sheets that remain on the gripper 54 and conveying the same to a given position. When using these apparatuses with a thin sheet, the bristles on the take-up rollers are likely to damage the sheet. The bristles also lack adaptability to the rigidity and pliability of the sheet, rendering a poor separation of one sheet from another.
Accordingly, there is a need for a stacked sheet separating and gripping apparatus that is capable of handling sheets of varying pliability and thicknesses, that is also simple in design and economical to manufacture.